This book primarily introduces innovative multi-physical plastic modeling for geomaterials in unsteady environments and advanced numerical methods for elastoplastic models, topics not systematically covered in other literature. The constitutive models in the form of stress-strain-environment will be interesting to students and researchers in geotechnical engineering and rock and soil mechanics. The book provides a thorough exploration of modeling techniques and algorithmic flowcharts, facilitating a deeper understanding of both theoretical models and numerical methods. It also guides readers in applying these tools to describe the mechanical behavior of geomaterials in various unsteady environments and addresses computational challenges in elastoplastic numerical analysis.